Answer: Mitral annular calcifications

Yes, this was a bit of an eye test but I wanted to make sure you all have seen these. They are not uncommon. Look for the thick “J” or “C” shaped calcifications overlying the region of the mitral valve, which progress to an full “O”. Although usually asymptomatic, they can be associated with mitral valve regurgitation and even heart block

reference: http://radiopaedia.org/articles/mitral_annular_calcification